1. Field of the Invention
This invention relates to novel oxabicyclo[3.1.0]hexan-2-ones, a process for their preparation and their use in a process for the preparation of dihalovinylcyclopropanecarboxylic acids.
2. Description of the Prior Art
Synthetic pyrethroid insecticides are esters which consist of an acid portion and an alcohol portion. In one group of pyrethroids disclosed in U.S. Pat. No. 4,024,163, the acid portion is derived from a 2,2-dihalovinylcyclopropanecarboxylic acid. Such an acid exists in the form of geometric isomers, in which the 2,2-dihalovinyl and the carboxyl groups are cis or trans to each other. Synthetic pyrethroids in which this acid portion is in the cis form are, in general, more active as insecticides than the corresponding trans compounds, and a great deal of research has been directed towards the preparation of cis 2,2-dihalovinylcyclopropanecarboxylic acids.
The applicant has now found a group of dihalolactones which are convenient to prepare and which can be converted readily into the desired cis dihalovinylcyclopropanecarboxylic acids.